The post from Jim Coleman, Sr. on tuning Acrosonics is fascinating. Equally fascinating to me is the simple fact that a number of the most popular models of pianos produced through the history of piano manufacturing have very uneven scaling through the tenor break. I speak of the Steinway M, the Baldwin Acrosonic, the Yamaha GH1... These are all _very_ successful pianos so we must by careful about how we discuss the tuning of these instruments. The tenor breaks on these pianos do not appear to have been an important factor when customers were making their purchasing decisions. Therefore, I would suggest that the discussion of how best to tune these instruments must be kept in its proper perspective, and that is that these tuning problems are almost certainly of more interest to us piano tuners than to our customers. Given that the inconsistency of inharmonicity through the scales of these pianos is so great, it should be on no surprise that tuners have different tastes and differing solutions to these tuning problems. Of course, these different solutions are worked out with great skill and effort and in the end conviction as well. They say you should not argue with someone who is smarter than you, so perhaps I would be better off not to disagree with Jim Coleman, Sr.! However, at the risk of coming out a distant second-best, I suggest that my approach to tuning these instruments is rather different from that of Jim Coleman, Sr., and my conviction that my approach is a correct one is as heartfelt as his as well. The matter of which partial from which to tune is a complex one. Jim suggests the fourth partial from A2-G#3. I would suggest that the third partial is a very good choice because it is a non-octave partial and will automatically compromise between the 2:1 and 4:2 octave relationships which is a significant benefit since the inharmonicity in the tenor can be so inconsistent. (This was covered in detail in my article in the January 1997 Journal; that's the Journal with Jim Coleman, Sr. on the cover!) Jim refers to the irregularity of the lower partials; I believe he is referring to the calculated Inharmonic Constant of a partial as it relates to the average calculated Inharmonic Constants of all the partials of a given string. My observations have been that there can be significant irregularity in both the 3rd _and_ 4th partials. "Inharmonicity Constant" is a calculation that according to theory says that if we know the relative pitches of two partials we can calculate the pitch of any other partial. The theory does not hold well on piano strings, but we are stuck with the term, unless we wish to start calling it the "Inharmonicity Non-constant". :) Mr. Coleman's suggestion for using different OTS numbers for different portions of the scale is interesting, and his description of the effects of doing so is entirely accurate. However, I have found that for my tastes conservative stretch is appropriate when tuning spinets and other very high inharmonicity pianos. (OTS 9 is not conservative.) My personal preference when dealing with a large difference in inharmonicity at the tenor break is to give up on smooth beat rates in the 3rds in favor of smooth beat rates in the 4ths, 5ths, and octaves. This can be accomplished by tuning through the break with the 3rd partial and an OTS 4, watching out for wound strings on the long bridge that may need to be raised slightly. (If these wound strings on the long bridge are too flat when the spinner is blushing, hit the octave up button and try halving the speed of the spinner. The display after hitting the octave up button is set on the third partial of the note an octave above which is the 6th partial of that wound string on the long bridge; the spinner will be spinning according to the width of the 6:3 octave.) The tuning calculator in Reyburn Cyber-Tuner, Chameleon 2, has a great deal of "smarts" programmed into it. The idea was to collect a good deal of data from a piano about its inharmonicity and then to use that data to calculate a tuning that would work for through the entire scale. Much design effort went into making Chameleon smart enough to calculate tunings for good well-scaled pianos and not-so-good not-so-well-scaled pianos alike. Large modifications to the calculated tunings are generally not needed in order to satisfy the tuning tastes of most tuners and their customers. Jim Coleman, Sr. wrote: >I thought some might like to try this approach on Acrosonics. > >For CyberTuners Only > >Special instructions for tuning 36" Acrosonics > >In my opinion if one tunes the temperament section using the 4th >partials, the higher inharmonicity pianos will smooth out better >across the Tenor stringing break. This however will involve using >two sparate tuning records when tuning pianos such as the Baldwin >Acrosonic spinet. > >Here is how I proceed: > >In Chameleon2 change from the default 3rd partial to the 4th partial >by clicking on the up/dn arrows in the 3rd section of partials. > >Sample the 5 A's in the normal manner. > >Click on OTS #9 and click on the chameleon Calculate button. > >Go back to Chameleon2 and click on OTS #4 and click on Calculate. > >This will allow you to tune from G3 (the lowest plain wire) thru C8 >using the tuning calculated with OTS 9 for all the plain wire notes. > >When tuning from F#3 downward, go back to the OTS 4 program. This >will make a very smooth transition across the break on this piano. >The wound strings will tune like 6-3 type octave matching. There >will be a couple of 5ths which are narrower than usual, but the >M3rds will be very well in line and the octaves will sound as good >as can be expected in a piano with this kind of break. > >If you don't like to tune the treble as sharp as I do, you could >select a 3rd tuning (OTS #6) for tuning from A4 up thru C8. Or, if >you are really conservative you could use the OTS #4 for the treble >from A4 thru C8. > >This general procedure should work well with most pianos which have >a hockey stick like curve in the Tenor bridge where there are wound >strings on that bridge. Use the higher OTS # for the plain strings >and use a much lower OTS for the wound strings. The differences may >need to be less between the two OTSs for some spinets, but it is >rather easy to discover what works best. > >partial 2 3 4 5 6 7 8 9 10 >C3 0.00 0.6 0.75 0.35 1.72 2.80 4.21 5.95 11.06 14.76 >Bass strings > >C#3 0.00 2.59 2.01 5.02 7.20 10.21 13.09 16.53 24.01 33.44 >Tenor >D3 0.00 2.17 4.08 4.62 7.29 10.21 13.31 4.93 24.76 34.80 >D#3 0.00 2.76 4.69 6.20 8.73 11.64 14.69 18.15 26.42 36.20 >E3 0.00 2.26 2.88 4.49 5.41 8.37 10.37 13.91 20.26 ? >F3 0.00 2.77 3.57 4.81 6.33 8.53 10.94 13.00 19.79 11.99 >F#3 0.00 4.10 4.81 5.95 7.44 9.20 11.33 14.03 ? ? > >G3 0.00 2.27 5.71 9.38 14.73 20.90 28.42 ? ? 48.43 lowest >plain >G#3 0.00 0.83 4.57 8.12 13.18 19.05 26.12 33.99 30.65 32.10 >strings >A3 0.00 1.57 3.90 7.34 11.92 17.17 23.72 30.99 48.19 68.96 >A#3 0.00 0.48 2.77 6.53 10.91 16.50 21.63 30.26 47.52 -8.25 >B3 0.00 1.85 3.86 7.23 11.31 16.40 22.25 28.90 44.30 -12.07 >C4 0.00 0.78 2.83 6.40 10.53 15.63 21.79 28.62 45.87 64.74 >C#4 0.00 1.55 3.86 7.54 11.77 17.07 23.31 30.44 5.34 -7.28 >D4 0.00 1.90 4.70 8.62 13.14 18.68 25.52 32.65 50.60 45.12 >D#4 0.00 1.10 5.03 8.33 12.85 18.14 24.62 30.49 48.92 69.20 >E4 0.00 0.30 4.00 7.83 12.35 17.89 24.54 32.07 49.80 -8.34 >F4 0.00 2.01 4.81 8.65 13.62 19.34 26.49 34.14 52.94 38.55 >F#4 0.00 2.26 5.04 9.14 14.80 21.07 28.79 37.34 57.94 29.03 >G4 0.00 3.51 6.72 11.18 16.84 24.03 32.06 41.64 ? ? >G#4 0.00 4.32 8.11 12.87 19.61 27.02 36.41 46.38 -2.35 23.31 >A4 0.00 1.06 4.87 9.31 15.72 22.86 31.78 41.64 -5.44 ? > >In this chart you can see the irregularity of the lower partials >especially. >This is good reason for tuning using the 4th partials in the temperament >area. > >Jim Coleman, Sr. > >
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